1. Field of the Invention
The present invention relates to a multi-functional image processing apparatus, and more particularly, to an image processing apparatus and an image processing method that reduce data transmission time by transmitting data between internal memories of a codec without passing through a system memory, and improve the processing speed by reducing the number of times the system memory is accessed. The present invention also reduces a load of a main processor for controlling the system memory when image data in binary form read by a sensor such as a charge coupled device is to be encoded, or decoded data transmitted from a JBIG codec or an MH/MR/MMR codec is to be encoded using another encoding method.
2. Description of the Related Art
In general, a digital copying machine or a digital multi-function machine performs various functions such as scanning, printing, copying, and fax transmitting/receiving. In order to perform these functions, an image processing apparatus includes a central processor, an image processor, a codec, and a memory unit. Recently, an application-specific integrated circuit (ASIC) performing all of the functions has been used.
FIG. 1 is a block diagram of a conventional image processing apparatus.
Referring to FIG. 1, the image processing apparatus includes a main processor 100, an image processor 105, a modified Hoffman (MH)/modified READ (MR)/modified MR (MMR) codec 104, a joint bi-level image experts group (JBIG) codec 103, and a printer interface 101.
The main processor 100 controls the entire image processing apparatus.
The image processor 105 converts analog data read by a charge-coupled device (CCD) 107 into digital data, performs a required image processing operation, and converts a continuous gray level value into a binary value.
The MH/MR/MMR codec 104 and the JBIG codec 103 encode or decode image data into or from MH/MR/MMR codec form or JBIG codec form.
In a scanning operation, sensing data read through the CCD 107 is transmitted to the image processor 105, and the data is transmitted from the image processor 105 to a system memory 102 controlled by the main processor 100 via a direct memory access (DMA).
In a printing operation, the data read by the system memory 102 is transmitted to the image processor 105, and the data output from the image processor 105 is transmitted to a printer engine unit 106 via the printer interface 101.
In a copying operation, the sensing data read by the CCD 107 is transmitted to the image processor 105, and image data output from the image processor 105 is transmitted to the printer engine unit 106 via the printer interface 101.
In a fax transmitting operation, the image data output from the image processor 105 or decoded data stored in the system memory 102 are encoded in MH/MR/MMR or JBIG form, and stored in the system memory 102, or transmitted externally.
In a fax receiving operation, data received is stored in the system memory 102, the MH/MR/MMR codec 104 or the JBIG codec 103 decodes the stored data and sends the decoded data to the printer engine unit 106 via the printer interface 101.
The fax transmitting/receiving operation is performed at 9600 bps via a general telephone line. Thus, in order to transmit a large amount of information data via a general telephone line, the amount of data representing the information should be as small as possible.
Therefore, the data is MH/MR/MMR or JBIG-encoded, and transmitted. Methods of transmitting/receiving the fax can be classified into a memory send/receive method and a direct send/receive method.
Memory Send/Receive Method:
A document is scanned, encoded, and stored by a sending side, and then sent to a receiving side. According to this method, the sending side and the receiving side should use a predetermined encoding method. Most general facsimiles use MH, MR, and MMR encoding methods, however, facsimiles supporting JBIG encoding have recently been developed. The JBIG encoding has a higher encoding rate than MH, MR, and MMR encoding, thus reducing the amount of sent data. The memory send/receive method is not effective if the sending side sends the document after MH, MR, or MMR encoding without considering the decoding operation of a receiving side that supports the JBIG encoding.
Direct Send/Receive Method:
The sending side recognizes the decoding method supported by the receiving side, and then transmits the data using the encoding method that can be decoded by the receiving side. If the receiving side supports JBIG encoding, the sending side JBIG encodes the data and sends the encoded data. According to the direct send/receive method, if the document scanned by the sending side is stored in the memory in JBIG form and the receiving side only supports MMR encoded data, or if the sending side wants to send the MMR encoded data as JBIG encoded data, the data must be decoded and re-encoded in a form that is supported by the receiving side. The decoding and re-encoding operations can be performed in the following way in the direct send/receive method.
When the main processor 100 transmits a decoding start message of page unit (DEC_SOP) to the MH/MR/MMR codec 104, the MH/MR/MMR codec 104 reads the MMR encoded data and stores it in the system memory 102. When the decoding operation is complete, the MH/MR/MMR codec 104 transmits an interrupt message (DEC_NT) that notifies the completion of the operation to the main processor 100.
Then, the main processor 100 transmits an encoding start message of page unit (ENC_SOP) to the JBIG codec 103, and the JBIG codec 103 reads the decoded data from the system memory 102, performs the re-encoding operation using the JBIG encoding scheme, and stores the encoded data in the system memory 102. When the re-encoding operation is complete, the JBIG codec 103 sends an interrupt message (ENC_INT) to the main processor 100.
When the fax is sent/received in the direct send/receive method, the encoding and re-encoding operations of the data stored in the system memory 102 should be performed.
For example, if it is assumed that the MMR-encoded document stored in the system memory 102 is re-encoded and sent, the MMR memory codec 104 directly reads the MMR-encoded data stored in the system memory 102 using a direct memory access (DMA) sending method. Then, the read data is decoded and transmitted from the system memory 102 using the DMA method. In addition, the JBIG codec 103 directly reads the decoded data using the DMA method to perform the encoding operation, and the encoded data is stored in the system memory 102 using the DMA method and transmitted to the receiving side.
Here, reading and storing processes of the data in the system memory 102 are required to decode the data, and the reading and storing processes must be performed to re-encode the data. Also, the main processor 100 must effectively control the data stored in the system in the decoding and re-encoding processes. Here, if the process of storing the decoded data in the system memory 102 and the process of reading the data from the system memory 102 can be removed, the number of times that the system memory 102 is accessed can be reduced, and the entire function of the system would be improved and the data stored in the system memory 102 could be easily controlled.
In the fax sending operation, transmit terminal identification (TTI) information is added to the top of the document being sent. The TTI includes date, time, company name, fax number, and machine identification. When it is assumed that the document data that will be sent is stored in the system memory 102 using the JBIG encoding method and the TTI is stored in the system memory 102 in a bitmap form, a new document is formed by adding the sending document to the TTI information and transmitted after being encoded.
Therefore, the encoded sending document data is decoded and stored in the system memory 102, the TTI information stored in the bitmap form and the decoded document are re-encoded and both stored in the system memory 102.
Thus, in the general image processing apparatus, the data encoded in a predetermined type or the image data input from the image processor is stored in the system memory in order to be encoded or re-encoded, and then the data stored in the system memory must be re-encoded. Thus, the load of the system memory increases, and the efficiency of entire system is lowered.
The present invention has similar features to Japanese Laid-open Patent No. Hei 07-307870, in that the compression data is code-converted in another compression method. However, the present invention provides an apparatus that can combine non-compressed data and compressed data, as well as an apparatus that code converts the compressed data.